Gian Marti

Last Name

Marti

First Name

Gian

ORCID

0000-0001-6848-0213

Organisational unit

09695 - Studer, Christoph / Studer, Christoph

Show all metadata

Search Results

Publications 1 - 10 of 28

Mitigating Smart Jammers in MU-MIMO via Joint Channel Estimation and Data Detection
Marti, Gian; Studer, Christoph (2022)
ICC 2022 - IEEE International Conference on Communications
Wireless systems must be resilient to jamming attacks. Existing mitigation methods require knowledge of the jammer's transmit characteristics. However, this knowledge may be difficult to acquire, especially for smart jammers that attack only specific instants during transmission in order to evade mitigation. We propose a novel method that mitigates attacks by smart jammers on massive multi-user multiple-input multiple-output (MU-MIMO) basestations (BSs). Our approach builds on recent progress in joint channel estimation and data detection (JED) and exploits the fact that a jammer cannot change its subspace within a coherence interval. Our method, called MAED (short for MitigAtion, Estimation, and Detection), uses a novel problem formulation that combines jammer estimation and mitigation, channel estimation, and data detection, instead of separating these tasks. We solve the problem approximately with an efficient iterative algorithm. Our simulation results show that MAED effectively mitigates a wide range of smart jamming attacks without having any a priori knowledge about the attack type.
Fundamental Limits for Jammer-Resilient Communication in Finite-Resolution MIMO
Marti, Gian; Stutz-Tirri, Alexander; Studer, Christoph (2024)
2024 58th Asilomar Conference on Signals, Systems, and Computers
Spatial filtering based on multiple-input multiple-output (MIMO) processing is a powerful method for jammer mitigation. In principle, a MIMO receiver can null the interference of a single-antenna jammer at the cost of only one degree of freedom - if the number of receive antennas is large, communication performance is barely affected. In this paper, we show that the potential for MIMO jammer mitigation based on the digital outputs of finite-resolution analog-to-digital converters (ADCs) is fundamentally worse: Strong jammers will either cause the ADCs to saturate (when the ADCs' quantization range is small) or drown legitimate communication signals in quantization noise (when the ADCs' quantization range is large). We provide a fundamental bound on the mutual information between the quantized receive signal and the legitimate transmit signal. Our bound shows that, for any fixed ADC resolution, the mutual information tends to zero as the jammer power tends to infinity, regardless of the quantization strategy. Our bound also confirms the intuition that for every 6.02 dB increase in jamming power, the ADC resolution must be increased by 1 bit in order to prevent the mutual information from vanishing.
Why maximum-a-posteriori blind image deblurring works after all
Marti, Gian; Ma, Boxiao; Loeliger, Hans-Andrea (2021)
2021 29th European Signal Processing Conference (EUSIPCO)
Maximum-a-posteriori (MAP) methods, while being a standard choice for many estimation problems, have been considered problematic for blind image deblurring: They have been suspected of preferring blurry images to sharp ones. Alternative methods without this apparent defect have been proposed instead. Reservations about MAP methods for blind image deblurring persist even as their close relation to these alternatives has become evident. We revisit the literature on this topic and argue that the original rejection of MAP methods was ill-founded. We show that the MAP approach can prefer sharp images over blurry ones. Furthermore, we show experimentally that the MAP approach can in principle achieve deblurring results that are competitive with the allegedly superior methods. We thereby challenge some traditional notions of the relevant causes underlying successful blind deblurring to obtain a more accurate understanding of the blind image deblurring problem.
Decoder-Assisted Communications over Additive Noise Channels
Bross, Shraga I.; Lapidoth, Amos; Marti, Gian (2020)
IEEE Transactions on Communications
A number of additive noise networks are studied in the presence of a helper that observes the noise and assists the decoder by providing it with a rate-limited description of said noise. It is shown that 'flash helping' - where noise descriptions are provided infrequently but with great precision - is often optimal and typically increases capacity by the maximal allowed description rate. It requires no binning. The discrete setting of the modulo-additive noise channel is also discussed.
High Dynamic Range mmWave Massive MU-MIMO with Householder Reflections
Palhares, Victoria; Marti, Gian; Castañeda Fernández, Oscar; et al. (2023)
2023 57th Asilomar Conference on Signals, Systems, and Computers
All-digital massive multiuser (MU) multiple-input multiple-output (MIMO) at millimeter-wave (mmWave) frequencies is a promising technology for next-generation wireless systems. Low-resolution analog-to-digital converters (ADCs) can be utilized to reduce the power consumption of all-digital basestation (BS) designs. However, simultaneously transmitting user equipments (UEs) with vastly different BS-side receive powers either drown weak UEs in quantization noise or saturate the ADCs. To address this issue, we propose high dynamic range (HDR) MIMO, a new paradigm that enables simultaneous reception of strong and weak UEs with low-resolution ADCs. HDR MIMO combines an adaptive analog spatial transform with digital equalization: The spatial transform focuses strong UEs on a subset of ADCs in order to mitigate quantization and saturation artifacts; digital equalization is then used for data detection. We demonstrate the efficacy of HDR MIMO in a massive MU-MIMO mmWave scenario that uses Householder reflections as spatial transform.
Single-Antenna Jammers in MIMO-OFDM Can Resemble Multi-Antenna Jammers
Marti, Gian; Studer, Christoph (2023)
IEEE Communications Letters
In multiple-input multiple-output (MIMO) wireless systems with frequency-flat channels, a single-antenna jammer causes receive interference that is confined to a one-dimensional subspace. Such a jammer can thus be nulled using linear spatial filtering at the cost of one degree of freedom. Frequency-selective channels are often transformed into multiple frequency-flat subcarriers with orthogonal frequency-division multiplexing (OFDM). We show that when a single-antenna jammer violates the OFDM protocol by not sending a cyclic prefix, the interference received on each subcarrier by a multi-antenna receiver is, in general, not confined to a subspace of dimension one (as a single-antenna jammer in a frequency-flat scenario would be), but of dimension L, where L is the jammer’s number of channel taps. In MIMO-OFDM systems, a single-antenna jammer can therefore resemble an L-antenna jammer. Simulations corroborate our theoretical results. These findings imply that mitigating jammers with large delay spread through linear spatial filtering is infeasible. We discuss some (im)possibilities for the way forward.
A Jammer-Mitigating 267 Mb/s 3.78mm² 583 mW 32 x 8 Multi-User MIMO Receiver in 22FDX
Bucheli, Florian; Castañeda Fernández, Oscar; Marti, Gian; et al. (2024)
2024 IEEE Symposium on VLSI Technology and Circuits (VLSI Technology and Circuits)
We present the first multi-user (MU) multiple-input multiple-output (MIMO) receiver ASIC that mitigates jamming attacks. The ASIC implements a recent nonlinear algorithm that performs joint jammer mitigation (via spatial filtering) and data detection (using a box prior on the data symbols). Our design supports 8 user equipments (UEs) and 32 basestation (BS) antennas, QPSK and 16-QAM with soft-outputs, and enables the mitigation of single-antenna barrage jammers and smart jammers. The fabricated 22 nm FD-SOI ASIC includes preprocessing, has a core area of 3.78 mm² , achieves a throughput of 267 Mb/s while consuming 583 mW, and is the only existing design that enables reliable data detection under jamming attacks.
Encoder-assistance for additive noise channels
Lapidoth, Amos; Marti, Gian (2021)
2020 IEEE Information Theory Workshop (ITW)
Flash helping has recently been shown to be an effective technique for describing additive noise to a decoder. It is shown here to be effective also in assisting the encoder: it achieves the helper capacity on the single-user Gaussian channel, on the multiple-access Gaussian channel, on the Exponential channel, and on the discrete modulo-additive noise channel. Most of the results hold irrespective of whether the helper observes the noise causally or noncausally.
Jammer Mitigation via Beam-Slicing for Low-Resolution mmWave Massive MU-MIMO
Marti, Gian; Castañeda Fernández, Oscar; Studer, Christoph (2021)
IEEE Open Journal of Circuits and Systems
Millimeter-wave (mmWave) massive multi-user multiple-input multiple-output (MU-MIMO) promises unprecedented data rates for next-generation wireless systems. To be practically viable, mmWave massive MU-MIMO basestations (BSs) must rely on low-resolution data converters which leaves them vulnerable to jammer interference. This paper proposes beam-slicing, a method that mitigates the impact of a permanently transmitting jammer during uplink transmission for BSs equipped with low-resolution analog-to-digital converters (ADCs). Beam-slicing is a localized analog spatial transform that focuses the jammer energy onto few ADCs, so that the transmitted data can be recovered based on the outputs of the interference-free ADCs. We demonstrate the efficacy of beam-slicing in combination with two digital jammer-mitigating data detectors: SNIPS and CHOPS. Soft-Nulling of Interferers with Partitions in Space (SNIPS) combines beam-slicing with a soft-nulling data detector that exploits knowledge of the ADC contamination; projeCtion onto ortHOgonal complement with Partitions in Space (CHOPS) combines beam-slicing with a linear projection that removes all signal components co-linear to an estimate of the jammer channel. Our results show that beam-slicing enables SNIPS and CHOPS to successfully serve 65% of the user equipments (UEs) for scenarios in which their antenna-domain counterparts that lack beam-slicing are only able to serve 2% of the UEs.
Other Helper Capacities
Lapidoth, Amos; Marti, Gian; Yan, Yiming (2021)
2021 IEEE International Symposium on Information Theory (ISIT)
The erasures-only capacity, the listsize capacity, and the cutoff rate are computed for the modulo-additive noise channel with a helper. In one scenario the helper provides a rate-limited description of the noise sequence to the decoder and in the other to the encoder. In both scenarios the gains in these capacities thanks to the helper can exceed the helper's rate.

Publications 1 - 10 of 28

Gian Marti

Last Name

First Name

ORCID

Organisational unit

Filters

Search Results